1. Field of the Invention
This invention relates generally to lancets and more particularly to novel, self-contained, precooked and single-use lancets which, when activated, extend a tip of a lancet blade outward from a lancet housing and back into the lancet housing for safe disposal.
2. Related Art
In particular, U.S. Pat. No. 5,514,152, issued to Roger E. Smith (Smith) May 7, 1996, discloses a lancet having a cocked torsion spring wound about a centrally disposed hub frangibly connected to a lancet housing. In a plural lancet strip embodiment, the lancet housing is disclosed to be a container for a plurality of lancets, each of which, after use, is frangibly separated from the rest of the strip and individually discarded. The spring is directly interconnected to a lancet blade in a cam/cam follower relationship which is taught to dispose the blade outwardly and inwardly in a substantially linear fashion. When the hub is frangibly separated from the lancet housing, the cocked spring is released to drive a lancet blade tip linearly from the lancet housing and then returned it back into the lancet housing.
Smith discloses frangible separation of the hub from the lancet housing where a base of the hub is annularly connected by sharp corners to the lancet housing. Smith also teaches that stress placed upon the base causes the hub to frange from the lancet housing, permitting a lancing cycle to begin. Before each lancing cycle is initiated, a lancet housing exit is exposed to provide an orifice through which the lancet blade tip travels. It is only when the orifice is provided that the sterility of the package is compromised keeping the blade and internal contents sterile until the orifice is opened.
U.S. Pat. No. 4,643,189 issued to Michael Mintz Feb. 17, 1987 (Mintz) discloses a concept for apparatus for implementing a skin incision which has been applied to a lancet application, particularly to a pediatric lancet, distributed under the name Tenderfoot.RTM. by International Technique Corporation, 23 Nevsky Street, Edison, N.J. 08820. This skin incision apparatus comprises a pivotal arm to which a lancing blade is securely affixed and which is driven by a torsion spring. The arm communicates with a surrounding lancet housing at two points, a first point at which is formed a sliding pivot disposed within the lancet housing and a second point which is within a track forming a cam follower arrangement. The arm is driven by the torsion spring to follow the track while sliding transversely to a patient contacting surface through which the blade communicates through a slot in the lancet housing. Thus, a portion of the arm and entire blade moves transversely in the direction of that portion of the arm which resides within the lancet housing between the pivot point and slot. In this manner, an elongated incision, having a controlled depth of cut is made through the surface of the skin. It is important to note that the length of the incision at the skin surface is substantially the same or longer than the length of the cut down below the skin surface, that the pivot is taught to be disposed more than a blade length away from a point of the blade.
In all other known lancets, both safety and non-safety types, it is a common practice to lance the exterior (epidermis) of the skin to reach the capillary rich inner dermis skin layer with an incision which is substantially the same size or greater in the epidermis layer than the subsequent incision in the dermis layer. Of particular interest, in this regard, are the well known facts that there are no blood carrying vessels disposed in the epidermis layer and that the dermis layer generally comprises a capillary rich bed which is the primary target of each lancet.